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rick
I know that making the mold is a pain but this sounds like a
great oportunity for the kids to get involved. I have had some good success
using low density foam for the fillers and have even used paper machey over
chicken wire before.
I assume you know that
fiberglass shrinks as it cures and can compress a male mold tight
espescially if you dont use enough pva or if you try to go orver 270 degrees of
radius. all of the nose cones that i build are two pieces then joined for
that reason
start with the bucking frames
for the support of the outer shell of the mold
I assume that you are trying a for true hemisphere
at this point if you are tyring for a modified shape like the k 350 fairing as
long a the center line of the radus stays the same this trick will
still work. stuff the mold voids with anything untill you are about a 1/4 inch
shy of the inner surface of the fairing. i forgot to say to make a radius
block for the design shape with a mount point at the center of the bucking
blocks and the lower edge. now apply the expanding foam to the out side.
after hard trim to match radius block. apply a thin coat of bondo to the surface
to fill any voids and seal the surface. Fair the mold again rember that we will
only be using a little over half of the mold for about 190 degrees of the
radius. glass the mold using thin bi directional cloth. fair again. apply the
final coat of resin and do not touch anymore the mold is done. remember that
most of the material in this mold are flamable so slow cure resins are prefered
less you want a nice fire.
time to start on the fairing.
apply pva to the mold, be generous this is the release agent. after dry apply
the first coat of glass and continue to build to the desired thickness . matt
can be used but will require more fairing. caution low blushing resins or
laminating resins should be used at this point. or just dont stop untill all
layers are applied. with the dried fairng still on the mold mark for edge cuts
and final fair. remove from the mold trm edges and install any internal supports
as needed.
i know that this sounds like a
lot of work but it really is not.
the frames are just circles of
3/4 ply spaced about 12 inches apart with a dowel running up through the center.
fillers can be chicken wire and paper machey/ styrafoam basically any thing that
is light wieght and some what ridgid. expanding foam any hardware store. bondo
any auto paint store
rick m
----- Original Message -----
Sent: Tuesday, December 06, 2005 11:00
AM
Subject: Re: [PSUBS-MAILIST] making
hemispheres [was "manipulator arms"]
An idea I've considered is buying a large
exercise ball and inflating it till it was quite firm. I'd use that as
the male mould. Take the female off that one and use it every time I'd
need to rebuild the nosecone. Like when my obstacle avoidance sonar
failed.
Needless to say it wouldn't have any surface
patterns, ribs, seams, etc. At least I'd try to get a seamless
one. Less work later on to grind off funny lines and "made in China"
labels.
One consideration is that the ball would probably
not be to scale. Could possibly use only part of the arc of the ball for
the nosecone. That way the scantlings could be faired into the
cone.
Rick L.
Vancouver
----- Original Message -----
Sent: Sunday, December 04, 2005 3:37
AM
Subject: RE: [PSUBS-MAILIST]
manipulator arms
As a matter of fact Rick, check out Brian Lula's observatory construction
pics for ideas on your spherical mockup. Not that second monster of his, but
the first one he built in his yard.
http://www.heavensgloryobservatory.com/
Ahh...too many interests, not enough life to do it all!
Joe
From: "Joseph Perkel" <joeperkel@hotmail.com>
Reply-To:
personal_submersibles@psubs.org
To:
personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST]
manipulator arms
Date: Sun, 04 Dec 2005 02:49:49
+0000
Rick,
"Want to start the hull mockup but have not
yet figured out how the make a hemisphere form plywood
yet."
There are good hints about this within the
homebuilt astronomical observatory community.
Joe
From: "rick miller"
<rickm@pegasuscontrols.com>
Reply-To:
personal_submersibles@psubs.org
To:
<personal_submersibles@psubs.org>
Subject:
[PSUBS-MAILIST] manipulator arms
Date: Sat, 3 Dec 2005
17:32:49 -0800
hi guys
I solved the rotation
problem and found a pump to use for the hydraulics. parker has a piston
pump that will withstand 500 psi on the inlet and is available in 48
volt dc so i can use a pressure comp resivor and flood the solinoids in
it. And using parker te series hyd motor for the rotation of the
claw i shoud be able to get about 2 - 10 rpm using a pwm for the motor
controller. i called alllen bradley about using one thier remote
i/o packages in the resivor, they had some missgivings about it,
but i figure if i epoxy encapsulate it it should live . That will save a
lot on hull pentrations because i will only have a power feed/ 2wire and
a data feed/2 wire. Still working on a budget price of about
2000.00$ for the parts for both. will start building the mockup soon.
Want to start the hull mockup but have
not yet figured out how the make a hemisphere form plywood yet. The
basic plan still calls for no mechanical hull pentrations. I also found
a great manufacture for brass and stainless hyd rams. the base pivots
and wrist pivot use off the shelf food grade pillow block bearings,
stainlesss and composite, wanting on the manufacturer to get back
to me with the mount strenghts.
rick
m
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